A jig is a device used generally to maintain the correct positional relationship between workpiece and a tool or between workpieces and parts of workpieces during assembly. The advantages of using jigs include obtaining more precise fits between workpieces when installed or assembled, repeatability in operations and standardization of products. Jigs are particularly useful in the construction trades, especially for finish woodworking, for making joints, including joints in moldings and trim boards.
One example of a portable jig for use in construction trades is provided by U.S. Pat. No. 4,629,171, disclosing a portable jig for assembling prefabricated building structures, particularly walls or similar structures. As with most jigs, an object of the '171 invention is to provide a means for assembling workpieces, in this instance walls, floors or similar structures, with ease, accuracy and low economic outlay. The disclosed jig basically comprises a plurality of cooperating tubular members and clamping members whereby a wall can be arranged in the necessary configuration for assembly.
Specialized jigs have been developed for specific purposes in construction finishing. The jig and template apparatus disclosed in U.S. Pat No. 4,102,374 is for preparing corner inserts for laminated plastic countertops. The apparatus includes a pair of scaffolds for supporting a countertop, male and female templates, and pneumatic cylinders for holding the countertops and templates together.
There are many commercially available general purpose templates and cutting guides including dovetail or box joint jigs, shelf drilling jigs, mortise and tenon jigs and various other jigs and templates. Many of these are designed to be used with a router. A router is a cutting tool comprising a base and a high-speed motor fitted thereon to rotate a cutting bit. A split collet chuck secures the bit and the depth of cut is adjusted by raising or lowering the motor in the base. Routers are commonly used to cut joints such as the dado, rabbit and mortis and tenon joints, to form or trim decorative edges, and to make molding or trim boards. The '374 patent discloses that the jig and template apparatus therein may be used with a router as the cutting tool.
Dispite the profusion of jigs and templates, there are some problems which have been unaddressed in the prior art. One such problem is to combine easy, convenient portability with a high degree fo repeatability and durability. A jig should be able to be moved very easily from workplace to workplace, occupy minimal set-up time, and yet ensure that work product accuracy and precision are not diminished.
Another problem is that many available jigs and templates require separate or supplementary clamping devices for holding the workpieces or templates. Such clamps are misplaced or forgotten easily and complicate transportation problems.
Known jigs and other equipment for making joints, such as miter boxes, address some of these problems and represent advances in the art. Such equipment may be used to produce stylized joints with an adequate degree of repeatability, but can not produce a customized joint, tailored to onsite factors such as the relationship, alignment and quality of the material and location of the workpiece.
With specific regard to preparing joints in molding and trim boards, particularly joints at baseboard inside corners, efficiency and economy would improve, along with precision, if an easily portable jig were available.
An easily portable coping jig for making joints in moldings and trim boards as precisely and accurately as possible, yet as quickly and efficiently as possible, would be a decided improvement over the jigs disclosed in the prior art.